Abstract: The ability of non-human primates to follow the gaze of other individuals has recently received much attention in comparative cognition. The aim of the present study was to investigate the emergence of this ability in a chimpanzee infant. The infant was trained to look at one of two objects, which an experimenter indicated by one of four different cue conditions: (1) tapping on the target object with a finger; (2) pointing to the target object with a finger; (3) gazing at the target object with head orientation; or (4) glancing at the target object without head orientation. The subject was given food rewards independently of its responses under the first three conditions, so that its responses to the objects were not influenced by the rewards. The glancing condition was tested occasionally, without any reinforcement. By the age of 13 months, the subject showed reliable following responses to the object that was indicated by the various cues, including glancing alone. Furthermore, additional tests clearly showed that the subject's performance was controlled by the “social” properties of the experimenter-given cues but not by the non-social, local-enhancing peripheral properties.

Abstract: This study was designed to examine whether chimpanzees and monkeys exhibit a global-to-local precedence in the processing of hierarchically organized compound stimuli, as has been reported for humans. Subjects were tested using a sequential matching-to-sample paradigm using stimuli that differed on the basis of their global configuration or local elements, or on both perceptual attributes. Although both species were able to discriminate stimuli on the basis of their global configuration or local elements, the chimpanzees exhibited a global-to-local processing strategy, whereas the rhesus monkeys exhibited a local-to-global processing strategy. The results suggest that perceptual and attentional mechanisms underlying information-processing strategies may account for differences in learning by primates.

Abstract: This study examined the communicative behavior of 49 captive chimpanzees (Pan troglodytes), particularly their use of vocalizations, manual gestures, and other auditory- or tactile-based behaviors as a means of gaining an inattentive audience's attention. A human (Homo sapiens) experimenter held a banana while oriented either toward or away from the chimpanzee. The chimpanzees' behavior was recorded for 60 s. Chimpanzees emitted vocalizations faster and were more likely to produce vocalizations as their 1st communicative behavior when a human was oriented away from them. Chimpanzees used manual gestures more frequently and faster when the human was oriented toward them. These results replicate the findings of earlier studies on chimpanzee gestural communication and provide new information about the intentional and functional use of their vocalizations.

Abstract: A large body of theoretical and empirical research suggests that kinship influences the development and maintenance of social bonds among group-living female mammals, and that human females may be unusual in the extent to which individuals form differentiated social relationships with nonrelatives. Here we combine behavioral observations of party association, spatial proximity, grooming, and space use with extensive molecular genetic analyses to determine whether female chimpanzees form strong social bonds with unrelated individuals of the same sex. We compare our results with those obtained from male chimpanzees who live in the same community and have been shown to form strong social bonds with each other. We demonstrate that party association is as good a predictor of spatial proximity and grooming in females as it is in males, that the highest party association indices are consistently found between female dyads, that the sexes do not differ in the long-term stability of their party association patterns, and that these results cannot be explained as a by-product of the tendency of females to selectively range in particular areas of the territory. We also show that close kin (i.e. mother-daughter and sibling dyads) are very rare, indicating that the vast majority of female dyads that form strong social bonds are not closely related. Additional analyses reveal that “subgroups” of females, consisting of individuals who frequently associate with one another in similar areas of the territory, do not consist of relatives. This suggests that a passive form of kin-biased dispersal, involving the differential migration of females from neighboring communities into subgroups, was also unlikely to be occurring. These results show that, as in males, kinship plays a limited role in structuring the intrasexual social relationships of female chimpanzees.

Abstract: Studies of ape tool use have been conducted in captivity since the early 1900s and in the wild since the 1960s. Chimpanzees are the most prolific tool users among the apes, and are known to use more tools than any other nonhuman animal. In contrast, reports of gorilla tool use are rare both in wild and captive settings. Studies of the processes involved in tool use learning have been limited in the wild by the lack of ability to control several unpredictable variables, and in captivity by tool use opportunities that are often presented in non-naturalistic contexts. We attempted to address both of these limitations by providing naïve subjects with a naturalistic tool use device (built to simulate a termite mound) while housed in a more natural social setting to approximate how learning would occur in the wild. Both gorillas and chimpanzees participated in the experiment to allow comparative analyses of acquisition of tool behaviour and the factors that may affect acquisition. Both species showed low frequencies of interaction with the mound in the baseline condition, before baiting with a food reward. Once baited, chimpanzees both attempted and succeeded to extract the reward more quickly than did gorillas. The number of social group members at the mound was significantly higher for chimpanzees than for gorillas and may have affected skill acquisition. We advocate that comparative approaches to skill acquisition and learning are valuable, but that researchers need to be cognizant of species differences in social structure that may affect results.